1. Field of the Invention
The present invention relates to a numerical control device with an interference check function.
2. Description of the Related Art
While a workpiece (machined object) is machined by a machining tool, each of the machine parts, such as a tool, table, jig for clamping the workpiece and spindle stock, inevitably interfere with each other. Hence, conventionally, an interference check to determine whether or not machine parts do not interfere with one another is made.
For example, Japanese Patent Application Laid Open No. H9-230918 discloses a method in which machine parts, such as tools, that are at a risk of interfering with each other are defined by a combination of several solid bodies and stored in memory as interference objects, and the positions of current interference objects, the displaced positions of axially displaced interference objects are found by interpolating movement commands and, in the displacement from the positions of the interference objects prior to interpolation to the positions of the interference objects following interpolation, the areas of interference of solid-body shapes constituting the interference objects are calculated as interference judgment solid bodies, interference judgment areas are established by means of a combination of interference judgment solid bodies, and the existence of interference is judged on the basis of the interference judgment areas thus established.
Furthermore, Japanese Patent Application Laid Open No. H8-115114 discloses a method that-establishes data for solid-body regions surrounding tools and data for entry prohibition areas, displaces the axes of the tools in accordance with a machining program, calculates the positions of current solid-body regions of tools from the current positions of the tool axes and the data for the solid-body regions surrounding the tools, and judges whether the current solid-body regions of the tools interfere with the entry prohibition regions.
Known machining tools include a 5-axis machining tool that comprises two rotational axes in addition to the feed shafts with the three basic X, Y and Z axes. FIGS. 17 to 19 show an outline of this 5-axis machining tool. In the case of the 5-axis machining tool shown in FIG. 17, a table 1 is driven in the direction of the X axis and in the direction of the Y axis, which is orthogonal to the X axis, and is rotatably driven about the A axis and B axis. A tool 2 is driven in the direction of the Z axis, which is orthogonal to the X axis and Y axis. The A axis is a rotational axis parallel to the Z axis, and the B axis is a rotational axis parallel to the X axis. FIG. 17 shows a state where a workpiece 4 is attached to the table 1 by means of a jig 3.
In the case of the 5-axis machining tool shown in FIG. 18, in addition to the table 1 being driven in the directions of the X and Y axes and tool 2 being driven in the direction of the Z axis, table 1 is rotated about the B axis and tool 2 is rotated (tilted) about the D axis. The B axis is a rotational axis parallel to the X axis and the D axis is a rotational axis parallel to the Y axis.
In the case of the 5-axis machining tool shown in FIG. 19, in addition to table 1 being driven in the direction of the X axis and Y axis and tool 2 being driven in the direction of the Z axis, tool 2 is also rotated about the C and D axes. The C axis is a rotational axis parallel to the Z axis and the D axis is a rotational axis that is disposed on plane XY.
Various types of 5-axis machining tools are known as mentioned above.
However, an interference check method that is suitable for the 5-axis machining tool described above has not been known yet. In the case of the interference check method disclosed by the Japanese Patent Application Laid Open No. H9-230918, in the displacement from the positions of interference objects prior to interpolation to the positions of the interference objects following interpolation, because the regions of interference of the solid-body shapes constituting the interference objects are calculated as interference judgment solid bodies, a complex calculation is required when this method is applied to a 5-axis machining tool, which makes this method unsuitable for a 5-axis machining tool.
Further, the interference check method disclosed by the Japanese Patent Application Laid Open No. H8-115114 can be applied to only a case where tool axes are displaced, and hence this method is not suitable for the variety of types of 5-axis machining tool mentioned above.
Meanwhile, in the case of a 5-axis machining tool, because the table, tool, and so forth are rotated and tilted, it is hard to estimate the positional relationships of the machine parts such as tools prior to machining, and interference between machine parts sometimes occurs when it is not expected during machining. When interference occurs between machine parts, machines, tools, or workpieces are damaged. For this reason, automatic interference checking for 5-axis machining tools is an essential task.